Samuel L Jackson has warned that Barack Obama should "be a leader" and stop "trying to relate".
The Pulp Fiction star took issue with the US President dropping the 'G's at the end of his words.
Jackson said: "We know it ain't because of his blackness, so I say stop trying to 'relate'. Be a leader. Be f***ing presidential."
Jackson continued his tirade, saying: "Look, I grew up in a society where I could say 'I ain't' or 'what it be' to my friends. But when I'm out presenting myself to the world as me, who graduated from college, who had family who cared about me, who has a well-read background, I f***ing conjugate."
Jackson, who campaigned for Obama in the 2008 presidential election, said he still thought the President was a "safe dude" but was aware he faced a difficult fight against the Republicans.
He said he thought Hillary Clinton would kick the Republican's "f***ing asses" if she decided to run for president in 2016.
He told Playboy magazine: "[Obama's] still a safe dude. But with those Republicans, we're now in a situation where even if he said, 'I want to give you mother***ers a raise,' they'd go, 'F*** you! We don’t want a raise!’
"I don’t know how we fix this bulls**t. How do we fix the fact that politicians aren't trying to serve the people, they're just trying to serve their party and their closed ideals?
"If Hillary Clinton decides to run, she's going to kick their f***ing asses, and those mother***ers would rather see the country go down in flames than let the times change."
The 64-year-old, who has been involved in US politics since the civil rights movement, added he was disillusioned with Facebook and Twitter petitions.
He said: "You need to have your physical body out there in the streets and let these people - and the rest of the world - know. When our anti-war movement led the world, it was because people could see us in the streets, see our faces, hear the protest music.
"You can’t do that s**t blogging in a room."